This invention relates to a reactor having a core formed of particles of iron or an iron-based magnetic material.
Recently a reactor having a constant inductance over a wide frequency range is widely used for various purposes. For instance, it is used to eliminate high frequency noises, to reverse current flow in inverter circuits using transistors, to protect electronic elements and to filter waves. Further it is employed as a transducer for thyristors.
The core of such a conventional reactor is made of, for example, ferrite, silicon steel plate or the like. Air gaps are arbitrarily provided on the magnetic flux path of the core, and the magnetic resistance in the air gaps determines the inductance of the reactor.
One of the known reactor is constructed as shown in FIG. 1. Its iron core 1 is made of ferrite, silicon steel plate or the like and has a cross section in the form of letter "I". A conductor is wound around the iron core 1 to form a coil 2. When the coil 2 is energized, a magnetic flux .phi. flows from the center of the iron core 1, through an upper flange of the core 1, through the air, through a lower flange of the core 1 and back to the center of the core 1. Another known reactor has an iron core constructed by two or more sections. Between any two adjacent core sections an air gap is provided, and around such iron core a conductor is wound to form a coil. When the coil is energized, a magnetic flux .phi. flows through the iron core and through the air gaps among the core sections.
The known reactors of the above-mentioned types are provided with only several air gaps to determine the inductance. The air gaps are necessarily be so wide as a few milimeters. Due to the wide air gaps a humming noise is generated or a considerable leakage of magnetic flux inevitably takes place in the air gaps when the coil is energized, thereby causing noises. Furthermore, since the air gaps determine the inductance of the reactor, an error in the air gaps, if any, will provide an erroneous inductance value. To provide a desired, predetermined inductance, the air gaps should be machined with a high precision.